Polishing pad and method for manufacturing polishing pads

ABSTRACT

A polishing pad comprising particles having an average diameter between 1 nanometer and 100 nanometers, wherein the total weight of the particles is greater than about 3% of the total weight of the pad. Also, a method of manufacturing a polishing pad comprises the steps of: mixing a pre-polymer and abrasive particles together; wherein the abrasive particles have an average diameter of between 1 nanometer and 100 nanometers in diameter, and wherein the abrasive particles comprise more than about 3% by weight of the polishing pad; mixing a curative with the mixed pre-polymer and particles; and pouring the mixture of pre-polymer, particles and curative into a mold. In one exemplary embodiment the particles are silica and the pre-polymer is a polyurethane pre-polymer.

FIELD OF INVENTION

The present invention generally relates to polishing materials, and more particularly, to polishing pads and methods for manufacturing the same.

BACKGROUND OF INVENTION

In the field of polishing, it is often important to obtain specific performance criteria for the rate of removal of material, the flatness of the polished object, and other such factors. These factors are often greatly impacted by the type of material used to polish an object. By way of example, polishing pads are often used in the semiconductor industry to polish raw wafers and for performing chemical mechanical planarization (“CMP”).

Many polishing methods and polishing materials involve the use of particles for abrading and/or polishing the surface of various materials and objects. For example, particles have been used in slurry to assist in CMP. In another example, particles are incorporated in the pad structure itself. In practice, the size of the particle and the amount of particles have been found to be particularly important in achieving desired polishing performance criteria. For example, large particles may inadvertently scratch the surface of the object being polished. Furthermore particles that are too small, or a small concentration of particles, may have a negligible impact on polishing.

In particular, it is desirable to use polishing particles having a diameter in the 1 to 100 nanometer size range. Particles smaller than 1 nanometer in diameter typically do not have a significant impact on removal rates. Furthermore particles that are larger than 100 nanometers may cause scratches in the polished surface that are unacceptable in size.

Use of particles having diameters between 1 nanometer and 100 nanometers has been successfully implemented in slurries. However, it is desirable for many reasons to reduce the amount of particles in a slurry by incorporating the particles into the pad itself. Moreover, desirable pad properties might be obtained if particles of this size are incorporated in the pad. For example, adding particles may cause a pad to be more hydrophilic.

Many attempts have been made by those in the art to make pads that are more hydrophilic. For example, different chemicals have been used, resin chains have been used, and other methods have been tried for increasing the hydrophilicity of pads. However, these methods resulted in the degradation of other pad properties even if they made the pad hydrophilic. A hydrophobic pad will bead water and the bead has a contact angle with the pad of greater than ninety degrees. In contrast, a water drop will ‘wet’ on a hydrophilic pad and will have a contact angle with the pad of less than ninety degrees.

Although various attempts have been made to construct a pad having particles of this size range, all of these attempts have not yielded a pad that can achieve desired performance criteria or that have desired mechanical properties.

In particular, it is known that adding silica particles to a mixture of pre-polymer and curative prior to placing the mixture in a mold can yield pads having abrasive particles (silica) imbedded within the pad material. However, prior attempts to utilize silica particles in the 1 to 100 nanometer range have not been able to produce finished polishing pads with a sufficient density, or percent by weight, of silica particles in this size range.

Indeed, the use of colloidal silica (i.e. silica particles in the 1-100 nanometer range) tends to cause the pre-polymer mixture to bind at relative silica concentrations above approximately (1-3%). In one experiment, the pre-polymer mixture becomes unworkable when the relative concentration of colloidal silica exceeds approximately (1%).

Thus, there remains a need for a polishing pad and method for forming a polishing pad, while still preserving polishing pad mechanical properties, where the pad includes particles between 1 nanometer and 100 nanometers in diameter. While particularly, a prior art pad and a method for manufacturing a prior art pad are needed which overcome the aforementioned binding problem observed in prior art processes.

SUMMARY OF INVENTION

A polishing pad comprises silica particles that have an average diameter of between 1 and 100 nanometers. The silica particles comprise greater than about 3%, by weight, of the pad. Also, a method of manufacturing a polishing pad comprises the steps of: mixing a pre-polymer and silica particles together; wherein the silica particles have an average diameter of between 1 and 100 nanometers, and wherein the silica particles comprises more than about 3% by weight of the pre-polymer/silica mixture. The method may further include the steps of mixing a curative with the mixed pre-polymer and silica, and pouring the mixture of pre-polymer, silica and curative into a mold.

In accordance with one aspect of the invention, abrasive particles (e.g. Silica) in a size range of 1-100 nanometers, and preferably in the range of about 30-50 nanometers, are added to the pre-polymer mixture prior to curing the pad material. In a particularly preferred environment, substantially all, or alternatively, a portion of the abrasive particles are coated prior to being added to the pre-polymer mixture.

In accordance with a further aspect of the present invention, the present inventor has observed that the use of coated abrasive particles in the colloidal size range tends to reduce the extent to which the pre-cured polymer mixture binds prior to curing, and therefore allows for greater concentration of silica particles than would be possible using non-coated abrasive particles within the same size range and concentration levels.

In accordance with a further aspect of the invention, the use of coated abrasive particles tends to reduce observed agglomeration within the mixture prior to curing, further facilitating the use of higher concentrations of abrasive particles than would be practical with uncoated particles of the same size range and concentration levels.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present invention may be derived by referring to the detailed description and claims when considered in connection with the Figures, wherein like reference numbers refer to similar elements throughout the Figures, and:

FIG. 1 is a flow diagram showing the steps of manufacturing an exemplary polishing pad, in accordance with an exemplary embodiment of the present invention; and

FIG. 2 is a block diagram showing an exemplary polishing pad, in accordance with an exemplary embodiment of the present invention.

DETAILED DESCRIPTION

While the exemplary embodiments herein are described in sufficient detail to enable those skilled in the art to practice the invention, it should be understood that other embodiments may be realized and that logical and mechanical changes may be made without departing from the spirit and scope of the invention. Thus, the following detailed description is presented for purposes of illustration only and not of limitation.

In accordance with various exemplary embodiments of the invention, a polishing structure comprises a concentration of particles such that the weight of all of the particles in the pad is greater than 3% of the weight of the pad. The polishing structure further comprises particles of a diameter between 1 nanometer and 100 nanometers, and preferably in the range of 30-50 nanometers, depending on the desired abrasive characteristics of the finished pad. The polishing structure furthermore maintains desirable mechanical properties while achieving these concentrations of particles in this range.

In accordance with one aspect of the invention, the polishing structure (pad) not only maintains desirable mechanical properties, but the addition of the abrasive particles tends to increase the hydrophilicity of the pad. Improving the hydrophilicity of the finished pad structure, whether the pad was initially hydrophobic or hydrophilic, has many advantages. For example, it has been observed that enhancing the hydrophilicity of the pad tends to yield improved material removal rates and can enhance the hardness, compressibility, and flatness of the finished pad. Increased hydrophilicity has also been observed to increase the amount of slurry at the interface between the pad surface and the work piece surface, even when the work piece is loaded against the pad creating a high pressure interface.

Prior attempts to manufacture a polymeric polishing pad having concentrations of abrasive particles above about 1% have been unsuccessful. Pads have been manufactured with particles sizes in the range of 1 to 100 nanometers in diameter; however, these pads have had less than 3% concentration of particles. Stated otherwise, prior art attempts to incorporate particles of this size range failed above a 1% concentration. Specifically, the mixture tended to render the pre-cured polymer mixture unsatisfactory because it became too stiff, too viscous, or simply too difficult to work with. While even at this low concentration, the finished pad may exhibit some enhanced mechanical properties, it is believed that the use of abrasive particles in concentrations greater than around 3%, result in a finished pad having significantly enhanced performance characteristics, such as material removal rate, slurry distribution, and the like.

It has been suggested that the colloidal properties of particles in the 1-100 nanometer size range may impede the ability to employ concentrations greater than approximately 1%. While particularly, particles in the 1-100 nanometer size range are often referred to as colloidal particles, or colloids, which are typically larger in size than particles found in solutions yet smaller in size than particles found in suspensions. In the context of this description, the term colloid or colloidal particle also implies that the particle is an ion, i.e., it exhibits a polar character. The magnitude of the polarity may of course vary with the size or type of particle employed, such as alumina, zirconia, zinc oxide, ceria, tin oxide, antimony, indium tin oxide, antimony tin oxide, titanium dioxide, silica dioxide, or the like.

Colloids in suspension exhibit a gelatinous or ‘jello-ish’ like physical character. The nature of a colloidal suspension results from the ionic charge on the surface of each particle, called the ZETA Potential. The ZETA Potential associated with particles in the 1 to 100 nanometer size range is believed to produce the gelatinous characteristic often associated with colloidal suspensions. See, for example, “Understanding Colloidal Suspensions”, http://www.hbci.com/˜wenonah/info/colloid.htm.

Present inventors have observed that the use of abrasive particles in the colloidal size range enhances the performance characteristics of the finished pad. However, particles in this size range tend to bind up the pre-polymer mixture at concentrations greater than 1%. In order to reduce the stiffening, binding, and/or agglomeration effect associated with the use of abrasive particles in concentrations greater than 1%, the present invention provides for the use of coatings or shells around some portion of or substantially all of the abrasive particles prior to introducing the particles into the pre-polymer mixture. In accordance with one aspect of the present invention, the thickness of the coating or shell does not appreciably affect the size of the particle; alternatively, the type and thickness of the coating may be engineered to tune the size and physical characteristics of the resulting coated particles.

The present invention thus provides a method for creating a polishing pad that includes particle sizes between 1 and 100 nanometers, at concentrations greater than 3%, and does so while preserving the ease of manufacture and the structural integrity/macroscopic properties of the finished pad.

In accordance with an exemplary embodiment of the present invention, the reduction of agglomeration among the reactants and the abrasive particles may also mitigate the binding problem discussed above.

In accordance with the present invention, various methods may be used to reduce/eliminate the agglomeration, and/or binding effects of the abrasive particles, the gelatin effect produced by colloidal suspension, and other undesirable effects associated with particles in the 1-100 nanometer size range. In accordance with an exemplary embodiment of the present invention, the particles are coated. Exemplary coating methodologies are described in detail in U.S. Pat. No. 6,537,665, assigned to Nyacol Nano Technologies, Inc., by O'Connor, et al., and incorporated herein by reference. The coated particles may be employed with minimal agglomeration during manufacture of polishing pads.

Furthermore, in accordance with another aspect of the invention, all of the particles to be mixed with the pre-polymer are coated. However, in other exemplary embodiments, only a portion of the particles are coated. Thus, some of the particles that are mixed with the pre-polymer are coated and others are not. In yet a further embodiment, the coating of the particles may be a partial coating, i.e., the coating may not fully prevent agglomeration but may reduce the amount of agglomeration that takes place. Thus, in various exemplary embodiments, agglomeration may be prevented or may be reduced. The reduction of agglomeration thus facilitates increasing the ratio (by weight) of particles in the pad.

As discussed above the particles may be coated using any desirable process, such as those described in the O'Connor, et al., patent. For example, a negatively charged silica hydrosol may first be coated with a hydrous oxide layer which reverses the polarity of the particle and provides a surface capable of reacting with an organic acid. The modified particle is thereafter coated with an organic acid, for example by treatment with an amphiphilic surfactant of an organic acid. Depending on the concentrations, chemistries, and materials employed, the resulting coating may render the abrasive particle non-polar and thus dispersible with minimal agglomeration in a non-polar solvent or polymer mix. Alternatively, the coating process and coating materials may be engineered to produce a desired residual polarity in the coated particle. Similarly, the coating materials and processes may be tuned to produce particles of virtually any desired size range and resulting polarity to achieve optimum performance characteristics of the finished pad.

In this regard, those skilled in the art world will appreciate that abrasive particles of a given size (for example in the 1-100 nanometer range) and of a given polarity in isolation may react with and/or combine with other particles during the pad manufacturing process. Depending on the nature of the other pad materials with which the abrasive particles are used, the size and/or polarity of the abrasive particles may undergo further refinement once the coated particles are incorporated into the mixture during pad manufacture. Accordingly, the coating process may be adapted to the particular environment in which the coated particles are to be added, so that particles of optimal size and ionic characteristics are ultimately reduced in the finished pad.

In accordance with an exemplary embodiment of the present invention, a pad 200 comprises particles 210 having a coating 211 in a matrix of pre-polymer material 220. The pad is configured to have greater than approximately 3% of the weight of the pad comprise the weight of all of the particles 210 in pad 200. More preferably, the particle weight percentage is greater than 15% of the pad weight, and even more preferably the particle weight percentage is greater than 25% of the pad weight. By way of contrast, in prior art attempts to mix 1-100 nanometer diameter uncoated particles into the base resin of polishing pads, the limiting factor was that it has not been possible to get above the critical threshold of a 1% to 3% concentration of those particles and still avoid binding during the mixing process.

Although described herein primarily as a pad for performing CMP (e.g., copper, oxide, metals, organic films, metallic-organo films, titanium, aluminum, deposition layers, sputtered layers, grown layers, and/or the like), those skilled in the art will appreciate that various materials which may be used for various tasks may benefit from this invention, whereas before it was not known how to make such materials. For example, the device may be a linear polishing material, a rotary polishing pad, belt type, disc, square, oscillating, rotating/oscillating, and/or other polishing devices where there is relative motion between the work piece and the pad promotes abrasion of the work piece. Similarly, the material may be used for such tasks as: polishing, material removal, CMP, lapping, grinding, and/or the like. Therefore, pad 200 may be any suitable device/material that is configured to perform such tasks.

Furthermore, the device/material may be suitable for use in connection with a variety of objects/materials. For example, the device may polish and/or remove material from wafers such as silicon wafers, substrate wafers, GaAs wafers, Indium phosphide wafers, glass wafers, safire wafers, and Silicon Carbide wafers. Moreover, the device may be used to polish and/or remove materials on glass, Liquid Crystal Displays, Optics, and/or the like. In addition, the device may be used on any materials that may benefit from polishing or material removal.

Particles 210 are preferably configured to have an average size (often referred to as diameter) of between 1 and 100 nanometers, more preferably between 30 and 100 nanometers, and more preferably still between 40 and 100 nanometers. In general, the particles may be of any size that yields desirable material removal characteristics when mixed with the pad material.

The particles may be any suitable abrasive, such as: silica, silica dioxide (SiO2), diamond, alumina, ziconia, zinc oxide, ceria, cerium oxide, tin oxide, antimony, indium tin oxide, antimony tin oxide, titanium dioxide, and/or the like. Particle 210 may further comprise any suitable abrasive particle. In one exemplary embodiment, particle 210 is any colloid particle.

In accordance with one aspect of an exemplary embodiment of the present invention, pre-polymer material 220 comprises a polyurethane pre-polymer, such as RN-1513, manufactured by Cytec in Olean, N.Y. In other exemplary embodiments, pre-polymer material 220 may comprise a polycarbonate, poly ethylene, and/or other pre-polymers that are suitable for use as a polishing pad. Furthermore, the present invention contemplates various combinations of various types of ingredients including: pre-polymer resins, abrasives, surfactants, blowing agents, curatives, and other ingredients used in making polishing pads.

In accordance with another exemplary embodiment of the present invention, and with reference to FIG. 1, a method 100 for creating a pad comprises the steps of: mixing a pre-polymer resin material and an abrasive particle material (step 110), adding a surfactant, blowing agent, and/or curative to the particle/pre-polymer mixture and mixing this combination (step 120), and pouring the resulting mixture into a mold (step 130). Method 100 may further comprise the steps of curing the mixture in the mold (step 140), and slicing the cured block (step 150) to create individual pads. However, those skilled in the art will recognize that other steps may be used in place of steps 120-150 to create pads or to create other kinds of polishing devices/materials.

Although method 100 describes a method associated with cast polyurethane pads, it should be appreciated that other methods of forming pads and/or mixing reactants may be used applying the principles of this invention. For example, pads may be manufactured using reaction injection molding, where the pad contains coated particles as described herein. Other examples of pad forming methods include: static mixing heads, use of a fiberglass chopper gun type device, single shaft open high or low shear dispersion, single shaft closed vacuum high or low shear dispersion, multi-shaft open and closed vacuum mixing, impingement mixing, and high and low speed closed inline mixing. Furthermore any suitable mixing devices and methods may be used in exemplary embodiments of the present invention.

The mixing step (step 110) involves measuring an amount of pre-polymer resin material (such as RN-1513, manufactured by Cytec), measuring an amount of particles, and mixing the pre-polymer and particles. Various particle types that may be used include: Nyacol Highly Dispersible Silica (HDS), model numbers 2942 or 6245; Nyacol Nucleator Grade Silica (NGS), model numbers 1000 or 2000; Nyasil 5, Nyasil 20, and Nyasil 6200 (silica additives); Nyacol colloidal ceria CeO2; Nyacol AL20 and AL20SD Alumina; all manufactured by Nyacol Nano Technologies, Inc. Other coated type particles may also be used.

In one exemplary embodiment, the particles are greater than 3% of the combined weight of the two materials. More preferably, the particles comprise greater than 25% of the combined weight of the two materials, and even more preferably greater than 40%.

In accordance with various exemplary embodiments of the present invention, a pad formed having particles 210 of an average diameter of 1 to 100 nanometers, with a greater than 3% concentration of those particles may exhibit several desirable qualities. The pad may be more hydrophilic than a similar pad without particles, the pad may be hydrophilic with the particles where it would be hydrophobic without the particles, the pad may exhibit an increased polishing rate, higher density, increased hardness, flatness, and uniformity.

In one exemplary comparison, a standard LP-57 pad has a density of 30 pounds/cubic feet, whereas the same pad including colloidal silica particles at greater than 3% of the weight of the pad has a density of 34 pounds/cubic feet. Similarly, the standard pad has a hardness (D) of 32 and the colloidal silica pad had a hardness of 35. In addition, the standard pad had a compressibility (at 5161 gram-force/square centimeter) of 8.3% and the colloidal silica pad had a compressibility of 7.9%. Other possible benefits include the ability to reduce the quantity of silica in the slurry. The polished object is also less likely to be scratched.

Furthermore, it should be appreciated that pad 200 may be a filled pad. For example, pad 200 may comprise particles having a diameter of 0.5 to 5 microns, or other suitable sizes. Filled pads are known in the art, however, the filled pad may be improved by adding coated particles that have an average diameter of 1 to 100 nanometers.

By way of example, several exemplary embodiments are provided herein. In accordance with an exemplary embodiment of the present invention, a method is provided for tuning the material removal rate of a polishing pad on a workpiece, said polishing pad having embedded therein coated abrasive particles characterized by average diameters in the range of 1 to 100 nanometers, the method comprising the steps of: a) providing a first polishing pad comprising a first quantity of coated particles having an average polarity of −X; b) measuring the material removal rate of said first pad on a workpiece under CMP conditions; c) providing an adjusted pad comprising a second quantity of coated particles having an average polarity of −Y; d) measuring the material removal rate of said adjusted pad on a workpiece under CMP conditions; and e) repeating steps c) and d) until a desired material removal rate is achieved.

In accordance with an exemplary embodiment of the present invention, a method is provided for tuning the material removal rate of a polishing pad, wherein the polishing pad comprises a plurality of abrasive particles, and wherein the plurality of abrasive particles have an average diameter of 1 to 100 nanometers. The method may comprise the steps of: tuning the polarity of at least a portion of the plurality of abrasive particles, wherein the tuning is configured to obtain an optimal material removal rate or increase material removal rate, and wherein the tuning includes reducing the absolute value of the polarity of at least a portion of the plurality of abrasive particles. In one exemplary embodiment, the polarity is reduced to near zero. In another exemplary embodiment, the tuning comprises coating the particles, and the coating is configured to modify the polarity of the particle and to facilitate mixing of the particles in concentrations greater than 25% by weight in the polishing pad.

In yet another exemplary embodiment, a method is provided for tuning the material removal rate of a polishing pad. The method may comprise the steps of: selecting at least one type of an abrasive particle for incorporation of a plurality of the abrasive particles in the polishing pad; selecting the size of the abrasive particles, wherein the plurality of abrasive particles have an average diameter of 1 to 100 nanometers; selecting other materials used to form the pad, wherein one of the other materials is a pre-polymer; tuning the polarity of at least a portion of a plurality of the abrasive particles, wherein the tuning is configured to obtain an optimal material removal rate or increase material removal rate; and mixing the plurality of the abrasive particles with the other materials as part of the process of forming a polishing pad.

In accordance with another exemplary embodiment, the tuning further comprises the steps of: determining the pH of at least one of the other materials; determining the initial polarity of the abrasive particle when uncoated; determining the pH of final environment; determining the desired polarity of final coated particle; and, coating the particle to achieve a desired removal rate.

In accordance with another exemplary embodiment, a method of tuning the material removal rate of a polishing pad, comprises the steps of: providing particles with a polarity represented by the variable X, wherein the initial size of the particles is in the range of 1-100 nanometers; and coating the particles to cause the particle to have a new polarity represented by the variable Y, wherein the absolute value of X is greater than the absolute value of Y, and wherein the coating is configured to modify the polarity of the particle to facilitate mixing of the particles in concentrations greater than 25% by weight in the pad.

In accordance with another exemplary embodiment, the plurality of particles are approximately 50 nm surface-modified silica particles. The coating may be configured to modify the polarity of the particle sufficiently to facilitate mixing of the particles in concentrations greater than 25% by weight in the pad.

In accordance with another exemplary embodiment, the plurality of abrasive particles are silica particles coated with a coating, wherein the plurality of abrasive particles are formed of a particulate powder adapted for dispersion in organophilic polymers, the particulate powder being prepared from a sol precursor for the powder, the outer surface of the powder particles having a first coating containing a reagent providing a surface reactive to an organic acid or an organic acid derivative; and a second coating covering the first coating, the second coating containing an amphiphilic surfactant and the organic acid or organic acid derivative reactable with the reagent in the first coating, the coated powder being characterized as being fully dispersible in the organophilic polymers substantially free from any agglomeration of the powder particles and without any change of the particle size distribution of the sol precursor of the powder before drying of the precursor to prepare the particulate powder.

Furthermore, in other exemplary embodiments, the ultimate particles possess a mean particle size of between 1 and 100 nanometers, the powder is silica, and the reagent in the first coating comprises a reagent reversing the charge on the powder particles from an initial negative charge to a positive charge.

Moreover, in other exemplary embodiments, the reagent in the first coating makes the surface of the first coating reactable with an organic acid or an organic acid derivative; and the second coating comprises an organic acid or organic acid derivative and an amphiphilic surfactant, and the reagent in the first coating comprises a reagent reversing the charge on the powder particles from an initial negative charge to a positive charge.

In the foregoing specification, the invention has been described with reference to specific embodiments. However, it may be appreciated that various modifications and changes may be made without departing from the scope of the invention. The specification and figures are to be regarded in an illustrative manner, rather than a restrictive one, and all such modifications are intended to be included within the scope of invention. Accordingly, the scope of the invention should be determined by the appended claims and their legal equivalents, rather than by the examples given above. For example, the steps recited in any of the method or process claims may be executed in any order and are not limited to the order presented.

Benefits, other advantages, and solutions to problems have been described above with regard to specific embodiments. However, the benefits, advantages, solutions to problems, and any element(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as critical, required, or essential features or elements of any or all the claims. As used herein, the terms “comprises”, “comprising”, or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Further, no element described herein is required for the practice of the invention unless expressly described as “essential” or “critical”. 

1. A method of tuning the material removal rate of a polishing pad on a workpiece, said polishing pad having embedded therein coated abrasive particles characterized by average diameters in the range of 1 to 100 nanometers, the method comprising the steps of: a) providing a first polishing pad comprising a first quantity of coated particles having an average polarity of −X; b) measuring the material removal rate of said first pad on a workpiece under CMP conditions; c) providing an adjusted pad comprising a second quantity of coated particles having an average polarity of −Y; d) measuring the material removal rate of said adjusted pad on a workpiece under CMP conditions; and e) repeating steps c) and d) until a desired material removal rate is achieved.
 2. The method of claim 1, wherein said abrasive particles comprise silica particles.
 3. The method of claim 1, wherein said polarity is reduced to near zero.
 4. The method of claim 1, wherein said tuning comprises coating the particles, and wherein said coating is configured to modify the polarity of the particle and to facilitate mixing of said particles in concentrations greater than 25% by weight in the polishing pad.
 5. A method of tuning the material removal rate of a polishing pad, the method comprising the steps of: selecting at least one type of an abrasive particle for incorporation of a plurality of said abrasive particles in said polishing pad; selecting the size of said abrasive particles, wherein said plurality of abrasive particles have an average diameter of 1 to 100 nanometers; selecting other materials used to form the pad, wherein one of said other materials is a pre-polymer; tuning the polarity of at least a portion of a plurality of said abrasive particles, wherein said tuning is configured to obtain an optimal material removal rate (increase material removal rate); and mixing said plurality of said abrasive particles with said other materials as part of the process of forming a polishing pad.
 6. The method of claim 5, wherein tuning the polarity of said abrasive particles comprises coating the particles, and wherein the coating renders the residual polarity near zero.
 7. The method of claim 5, wherein said coating is configured to modify the polarity of the particle and to facilitate mixing of said particles in concentrations greater than 25% by weight in the pad.
 8. The method of claim 5, wherein said abrasive particle type is a silica particle.
 9. The method of claim 5, wherein said tuning further comprises the steps of: determining the pH of at least one of said other materials; determining the initial polarity of said abrasive particle when uncoated; determining the pH of final environment; determining the desired polarity of final coated particle; and, coating the particle to achieve a desired removal rate.
 10. A method of tuning the material removal rate of a polishing pad, the method comprising the steps of: providing particles with a polarity X, wherein the initial size of said particles is in the range of 1-100 nanometers; coating said particles to make the polarity Y, wherein the absolute value of X is greater than the absolute value of Y, wherein said coating is configured to modify the polarity of the particle and to facilitate mixing of said particles in concentrations greater than 25% by weight in the pad.
 11. The method of claim 10, wherein said initial particle size is in the range of 30 to 50 nanometers.
 12. The method of claim 5, wherein the coating renders the residual polarity near zero.
 13. The method of claim 5, wherein all of said particles are modified.
 14. The method of claim 5, wherein said polishing pad has an higher removal rate compared to a polishing pad that does not comprise coated particles.
 15. A polishing pad comprising: a pre-polymer, a plurality of particles mixed with said pre-polymer, wherein the plurality of particles have an average diameter of between 1 and 100 nanometers, and wherein the plurality of particles comprise greater than 3%, by weight, of the pad.
 16. The polishing pad of claim 15, wherein the pre-polymer is a polyurethane pre-polymer and wherein the plurality of particles are silica particles.
 17. The polishing pad of claim 15, wherein the pre-polymer is a polyurethane pre-polymer and wherein the plurality of particles are approximately 50 nm surface-modified silica particles.
 18. The polishing pad of claim 15, wherein the pre-polymer is a polyurethane pre-polymer and wherein the plurality of particles are configured to cause at least one of: a reduction in agglomeration, a reduction in binding due to colloidal forces, and a reduction in resistance to mixing of the pre-polymer and the poly urethane pre-polymer.
 19. The polishing pad of claim 15, wherein said coating is configured to modify the polarity of the particle and to facilitate mixing of said particles in concentrations greater than 25% by weight in the pad.
 20. A polishing pad comprising silica particles that have an average diameter of between 1 and 100 nanometers, wherein the silica particles are configured to facilitate a concentration of said silica particles in said pad, wherein said concentration of silica particles is greater than 3%, by weight, of the pad.
 21. The polishing pad of claim 15, wherein said concentration of silica particles is greater than 25%, by weight, of the pad.
 22. A method of manufacturing a polishing pad comprising the steps of: mixing a pre-polymer and silica particles together; wherein the silica particles have an average diameter of between 1 and 100 nanometers, and comprises more than 3%, by weight, of the pre-polymer/silica particles mixture; mixing a curative with the mixed pre-polymer and silica; and pouring the mixture of pre-polymer, silica and curative into a mold.
 23. A polishing pad comprising a plurality of abrasive particles, wherein each of said plurality of abrasive particles has a particle diameter, wherein the average particle diameter of said plurality of abrasive particles is between 1 and 100 nanometers, and wherein the combined weight of said plurality of abrasive particles in said polishing pad is greater than 10% of the weight of said pad.
 24. The polishing pad of claim 23, wherein said plurality of abrasive particles comprise at least silica particles and wherein the polishing pad is configured to perform chemical mechanical polishing.
 25. The polishing pad of claim 23, wherein said plurality of abrasive particles are silica particles coated with a coating, and wherein said coating is configured to modify the polarity of the particle sufficiently to facilitate mixing of said particles in concentrations greater than 25% by weight in the pad.
 26. The polishing pad of claim 23, wherein said plurality of abrasive particles are silica particles coated with a coating and wherein said plurality of abrasive particles are formed of a particulate powder adapted for dispersion in organophilic polymers, the particulate powder being prepared from a sol precursor for the powder, the outer surface of the powder particles having a first coating containing a reagent providing a surface reactive to an organic acid or an organic acid derivative; and a second coating covering the first coating, the second coating containing an amphiphilic surfactant and the organic acid or organic acid derivative reactable with the reagent in the first coating, the coated powder being characterized as being fully dispersible in the organophilic polymers substantially free from any agglomeration of the powder particles and without any change of the particle size distribution of the sol precursor of the powder before drying of the precursor to prepare the particulate powder.
 27. A particulate powder as defined in claim 27 wherein the ultimate particles possess a mean particle size of between 1 and 100 nanometers, wherein the powder is silica, and wherein the reagent in the first coating comprises a reagent reversing the charge on the powder particles from an initial negative charge to a positive charge.
 28. An organophilic polymer having dispersed therein a powder as defined in claim 27, wherein the reagent in the first coating makes the surface of the first coating reactable with an organic acid or an organic acid derivative; and the second coating comprises an organic acid or organic acid derivative and an amphiphilic surfactant, and wherein the reagent in the first coating comprises a reagent reversing the charge on the powder particles from an initial negative charge to a positive charge.
 29. The polishing pad of claim 27, wherein said coating is configured to modify the polarity of the particle and to facilitate mixing of said particles in concentrations greater than 25% by weight in the pad.
 30. A polishing pad comprising silica particles, wherein the silica particles are greater than 3% by weight of the total weight of the pad, and wherein the polishing pad is more hydrophilic than a similar pad without the silica particles. 